Building an inline 6 Chevy 250 engine
From Crankshaft Coalition Wiki
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==Introduction== | ==Introduction== | ||
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| + | |[[File:250 w fi.jpg|thumb|center|285px|]] | ||
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| + | The Chevy inline 6 is a design that has been around in one version or another since 1929 until 1990 in North American-market vehicles. During the fall of 1961, an unrelated and more modern version of the six was introduced (with the Chevy II) which has 7 main bearings and a short deck displacing 194 c.i.d. - the rear block face was redesigned with a bell-housing pattern which matched the Chevrolet V8's in production (both the small block and W-series) - transmission bell-housings for the V8 (both manual and automatic) were shared. The Chevy straight 6 250 c.i.d. engine was brought out in 1966. It has a 0.280" longer stroke (3.53") and the same bore (3.875") as the 230 c.i.d. straight 6. It boasts a 7 main bearing bottom end- quite an improvement over the previous generation inline's 4 main bearings. Although production ceased in 1990 for automotive use, the inline six (including its four cylinder variant still in production as the Vortec 3000 marine/industrial motor) was produced overseas in Latin America for Brazilian-market GM products until the 2001 model year. 250 production ended in 1984 (North America only) but the 292 tall deck engine remained in production in Mexico until 2001. Besides Latin America (e.g. Brasil, Argentina) where the six was locally manufactured, it was also manufactured by GM's Port Elizabeth, South Africa assembly plant until the company divested from South Africa in the mid-1980's during the Apartheid regime. | ||
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| + | ==Some things to consider== | ||
| + | Building a straight 6 250 is not any harder to do than any other inline 6, be it a Ford or Chevy or, GMC, etc. Parts aren't as common for the inline 250 as they are for a SBC, but there is info and quite a few suppliers for parts, as well as places that cater to almost nothing but the Chevy inline 6 engines. | ||
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| + | The inline 6 Chevy 250 should not be compared to a SBC engine. Besides the obvious differences, they share practically no parts w/the V8 engines (save for the oil filter (AC Delco PF25 or equivalent) and some of the valve train (the rocker arms do not interchange with the Chevrolet V8 (all series). Because of this fact expect it to cost more per horsepower than a Chevy V8. The reward is this is not a "belly button" engine; instead it is considered "old school" and has cred because of what it "isn't" as much as for what it "is". | ||
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| + | To the right person, building a 250 Chevy 6 can be just as rewarding as any other engine, and if parts are selected in a coordinated manner and the engine used in a way that accentuates its strong suits- like dependability and good lower RPM torque production for its size- a very satisfying result can be had. | ||
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| + | It's a fool's mission to build a NA inline 6 like the Chevy 250 expecting to run amok on all the small block Chevy, Ford, and Mopars out there. Not only will the results be very humbling, but the amount of money that would need to be spent in order to go toe-to-toe with a SBC 350 will break most people's budget all to hell. So instead of trying to beat the world, it may be much more satisfying to build a Chevy 250 to make around 0.8-1 HP/c.i.d. (~200-250 HP), and revel in the uniqueness of it and enjoy as torquey, strong running engine that has a sound and look all of its own. | ||
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| + | Given enough time, effort and cash, an inline Chevy 6 can make >/= 2 HP/Ci naturally aspirated and far more than that using a turbocharger. Superchargers can also be used, but the turbo is the preference of many who are going for boost. | ||
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| + | ==Engine ID== | ||
| + | ===Casting numbers, date codes, and suffix codes=== | ||
| + | Obviously casting numbers and V.I.N. stampings can be a big help. Chevy inline 6 casting numbers can usually be found just above the starter on the passenger side of the block. | ||
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| + | On the block there will be foundry ID codes, for instance "CON3". This is no help in identifying the engine. | ||
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| + | There may be a date code cast into the block. Example- "A 30 2": Jan 30 of a year ending in 2. If the engine is a 250, that would be 1972. | ||
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| + | The suffix code (also called the "application" code) will be at the end of a string of letters and numbers (that's why it's called a suffix). The suffix string is usually a letter followed by a date code, followed by 1, 2 or 3 letter code. This is found in the area near the distributor, above the fuel pump. The suffix string of letters/numbers are always stamped in, not cast into the block like the date code or foundry ID code. | ||
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| + | There may also be a partial V.I.N. number stamped in a separate string of numbers near the suffix string. If the block is missing the suffix and partial V.I.N., there's no way to know what the engine might have come in originally, unless there were other external clues like a carb w/a governor on it (would be on a heavy truck or bus), or if it had a large bell-housing and a HD "granny low" trans (also HD truck/bus application). If the crankshaft has a pilot bushing in it, that would mean it had been used with a manual trans- although this could have been added later.<br> | ||
See '''[[Building an inline 6 Chevy 250 engine#Resources|below]]''' under '''Resources''' for sites that have casting number info. | See '''[[Building an inline 6 Chevy 250 engine#Resources|below]]''' under '''Resources''' for sites that have casting number info. | ||
===Deck height=== | ===Deck height=== | ||
| − | The deck height of the Chevy 230 and 250 inline 6 engines is shorter than the 292 inline 6 engine. That means the | + | The deck height of the Chevy 230 and 250 inline 6 engines is shorter than the 292 inline 6 engine. That means the push rod cover is shorter on those engines than on the 292 Chevy 6, as seen below. The RH engine mount is located a few inches forward of the smaller displacement engines. Some 292s (and a few 250s used in truck/van applications) used a 90 degree oil filter adapter where the filter is pointing downward (same as the Chevrolet V8) - these blocks have a 3 bolt boss (some blocks have this area unmachined where the holes can be drilled out). |
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|[[File:Vin stamp.jpg|thumb|300px|250 Chevy inline 6. Location of VIN/application code stamping for 1962 and newer engines is circled]] | |[[File:Vin stamp.jpg|thumb|300px|250 Chevy inline 6. Location of VIN/application code stamping for 1962 and newer engines is circled]] | ||
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==Cylinder heads== | ==Cylinder heads== | ||
| − | The integrated intake head isn't well suited for performance duty. About all that can be done for a head with this intake, is the 1 barrel can be swapped for a 2 barrel by using an | + | The integrated intake head used with the 250 (except the 292 which retained the separate intake) between 1975-1984 isn't well suited for performance duty. Some pundits claimed that the integrated cylinder head resulted in increased fuel economy and NVH (noise, vibration, and harshness), its another relic of the malaise era which lasted until late 1984 when the 250 was last optioned with the Chevrolet/GMC truck/van lineup until the 4.3L replaced it. About all that can be done for a head with this intake, is the 1 barrel can be swapped for a 2 barrel by using an adapter. Integrated intake cylinder heads had one-barrel carburetors until the 1979 model year (the light trucks with the 250 used a Rochester Varajet 2 barrel from 1979-84 which is not performance oriented. Not the hot ticket. The lump port mods along with porting, larger valves, etc. can be done to ANY head, but without the ability to use a high performance intake, these mods would be largely wasted. |
| − | Using the earlier head with the detachable intake from a 194, 230 or 250 | + | Using the earlier head (or one from a 1975-1990 tall deck 292) with the detachable intake from a 194, 230 or 250 c.i.d. inline Chevy 6 offers a much better platform. Because of the current lack of aftermarket support for inline Chevy 6 cylinder heads, the hot rodder is left with the removable intake head from the early/mid 70's as the best choice for performance use, unless the cost of a custom head can be justified. |
| − | In the past there were heads made for the Chevy 6. Now there are one-off heads for the Chevy inline 6 that have been made from 2 SBC aftermarket aluminum heads that have been divided and welded back together. | + | In the past there were heads made for the Chevy 6. Now there are one-off heads for the Chevy inline 6 that have been made from 2 SBC aftermarket aluminum heads that have been divided and welded back together. Another hybrid cylinder head is usually made from two Vortec 3.0 (181) used in marine or industrial applications - the 3.0 is based on the Chevrolet 153 engine first used in the 1962-67 Chevy II and some 1968-70 Novas (including the Chevrolet/GMC G-series vans (1964-66) and the Jeep DJ-5 (1968-70) used by the United States Postal Service). |
| − | A relatively easy to find head to swap on the 250 inline Chevy is casting number 3864883 from a 194 | + | A relatively easy to find head to swap on the 250 inline Chevy is casting number 3864883 from a 194 c.i.d. Chevy inline 6 engine. If it's milled 0.060", it will give about 10:1 compression on a Chevy 250 using stock type pistons. |
===One-off custom aluminum head=== | ===One-off custom aluminum head=== | ||
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Just goes to show you what can be done with enough skill, tools, time and dedication. | Just goes to show you what can be done with enough skill, tools, time and dedication. | ||
| − | [ | + | [Kay Sissell] has also done some custom heads for the inline Chevy six. He now offers ported cast iron heads and other parts. |
===Intake port mods=== | ===Intake port mods=== | ||
The Chevy 250 head has a "3-port" intake. That means two ports are siamesed into a single port. This design, while fine for a daily driver or truck, leaves a lot to be desired for high performance work. | The Chevy 250 head has a "3-port" intake. That means two ports are siamesed into a single port. This design, while fine for a daily driver or truck, leaves a lot to be desired for high performance work. | ||
| − | So it comes as no surprise that improving the intake port flow will help power. A big improvement to the Chevy inline 250 cylinder head is to install an intake port "lump". For years, these were one-off, hand-made pieces that were quite a chore to fabricate and mount. Some were better than others, and some were worse than nothing. Nowadays, [http://t6racing.org/index.html T6 Racing] and [http://www.12bolt.com/home | + | So it comes as no surprise that improving the intake port flow will help power. A big improvement to the Chevy inline 250 cylinder head is to install an intake port "lump". For years, these were one-off, hand-made pieces that were quite a chore to fabricate and mount. Some were better than others, and some were worse than nothing. Nowadays, [http://t6racing.org/index.html T6 Racing] and [http://www.12bolt.com/home 12Bolt] have designed a lump kit and can supply all the necessary tools and info to install it. It is cast and machined pieces of metal that fit onto the intake port floors to vastly improve flow. |
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|[[File:Top lump port w arrows.jpg|thumb|370px|left|Arrowed area has to be blended away]] | |[[File:Top lump port w arrows.jpg|thumb|370px|left|Arrowed area has to be blended away]] | ||
|[[File:Cutaway lump in port.jpg|thumb|290px|left|Cutaway showing lump in port]] | |[[File:Cutaway lump in port.jpg|thumb|290px|left|Cutaway showing lump in port]] | ||
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===Head torque specs=== | ===Head torque specs=== | ||
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==Intake manifolds== | ==Intake manifolds== | ||
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| − | + | Throughout its production life cycle, the inline 6 Chevrolet came with a one barrel carburetor (except for the 235" Corvette engine). Carter YF carburetors were used with the early engines until some point in the mid-1960's when the Rochester Monojet (1MV) was phased into production. The 1MV was used until the end of the 1979 model year (with passenger cars) but continued production with the 292 until its 1990 phaseout in North America and marine applications. Rochester 2SE (Varajet) was introduced in 1978 - only known vehicles using the Varajet were the C/K light duty truck (half ton) and G-series vans including the P series box vans. One drawback is the uneven fuel mixture with the stock one barrel carburetor where the front and rear cylinders have an uneven fuel distribution. | |
| − | The stock intake uses the exhaust manifold to provide heat to the intake, but if aftermarket exhaust headers and/or intake manifolds are used, this feature will be missing. For many applications that will see daily driver duty, an aftermarket intake equipped with hot water heating of the plenum is a plus. | + | Beginning in the mid-70's, the inline 6 Chevy (with the exception of the tall deck 292) got an integrated intake cylinder head similar in design to the Ford Falcon Six. This was a step in the wrong direction for a performance engine- the intake being cast as part of the head means it would take too much work to remove it to be able to use any kind of 4-barrel carb. There are three different designs for the integrated head - casting number #355795, #370696 was used with the mass market passenger cars e.g. X and F platform automobiles (Nova (includes its rebadged clones), Camaro) which has a wide footprint valve cover. A mid-cycle refresh in 1977 with casting number 377131 with the one barrel carburetor base continued in production until 1979 but used a valve cover sized similarly to the conventional head with a shorter height, smooth face, and the PCV tube behind the oil fill hole (a known visual cue which IDs an integrated cylinder head is the position of the PVC breather tube; the truck/van integrated head 250s after 1978 had a taller valve cover with internal baffles). Light duty trucks c. 1978 - 1984 will have casting 14015499 (this one has the Varajet carburetor base - integrated intake runners are curved and incorporate a dual outlet exhaust manifold). |
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| + | But the detachable intake head (3895052, 3895054, 3927763, 83413880) can be fitted with a large variety of intake manifolds from the cast iron stocker to custom EFI (including multi point fuel injection setups e.g. the use of Jeep 4.0 fuel injectors and the use of the Jeep throttle body requiring the use of a custom fuel rail and modifications to the intake manifold), IR, 4-barrels, staged 2 barrels, multiple carbs from Stromberg 94/97s to Weber's, to name a few. | ||
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| + | (GM Brasil did manufacture multi point fuel injection (with revised cylinder heads using the separate intake manifold) for the 250 - Brazilian market Chevrolet's (Brazil-market Chevrolet Omega and its local produced GMT400 trucks had the 250 (4.1L); production ended in 2001.) | ||
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| + | The stock intake uses the exhaust manifold to provide heat to the intake, but if aftermarket exhaust headers and/or intake manifolds are used, this feature will be missing (this setup is similar to a stock Jeep 4.0L (which is the final generation of the AMC inline six used exclusively by Jeep c. 1987-2006) where a tubular exhaust header is used in lieu of a cast iron manifold). For many applications that will see daily driver duty, an aftermarket intake equipped with hot water heating of the plenum is a plus. | ||
If making all the power possible is the goal, an intake without hot water heating would be the better choice. | If making all the power possible is the goal, an intake without hot water heating would be the better choice. | ||
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==Camshafts== | ==Camshafts== | ||
There are still manufacturers stocking cams for the Chevy inline engines. | There are still manufacturers stocking cams for the Chevy inline engines. | ||
| − | *[http://www.iskycams.com/onlinecatalog.html Isky catalog], see pages 126-127 | + | *[http://www.iskycams.com/onlinecatalog.html Isky catalog], see pages 126-127 |
==Timing gears== | ==Timing gears== | ||
| − | The Chevy inline 6 uses a pair of gears | + | The Chevy inline 6 uses a pair of gears instead of a chain to turn the camshaft. There are high performance gear sets available from Comp and others. The cam gear on aftermarket performance timing sets is often aluminum. The undesirable gear set with the micarta (plastic) cam gear is best avoided - these were used during the mid-1970's - mid 1980's with the 250 and 292 (including the Pontiac Iron Duke which shared its design with the 153 with the exception of a cross-flow cylinder head and repositioned distributor while using some components from the concurrent Pontiac 301) in both passenger cars and light trucks. |
==Exhaust manifolds== | ==Exhaust manifolds== | ||
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*[http://www.cliffordperformance.net/index.html Clifford Performance] | *[http://www.cliffordperformance.net/index.html Clifford Performance] | ||
*[http://sissellautomotive.com/ Sissells Automotive] | *[http://sissellautomotive.com/ Sissells Automotive] | ||
| − | + | *[http://www.12bolt.com/home 12Bolt] | |
{{youcanedit}} | {{youcanedit}} | ||
[[Category:Engine]] | [[Category:Engine]] | ||
[[Category:GM]] | [[Category:GM]] | ||
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